Particle-based display (PBD) technology has drawn a great deal of attention in display industries in recent years. Due to its wide viewing angles, low power consumptions, light weight, and thin thickness, PBDs have found widespread applications in a variety of fields, for example, in electronic readers, electronic papers, electronic tags, electronic signages, and the like. PBDs are capable of providing visual effects similar to that of paper reading. Different from backlight-type flat panel displays, PBDs utilize reflected ambient light from pigment particles to display content, and thus, there is no glare or other effects resulted from strong external light which affect reading. In addition, PBDs consume power only when the displayed contents are subjected to change.
A PBD includes a plurality of independently addressable display units spatially arranged in the form of a matrix. Each display unit is formed with a plurality of display cells, where each display cell is filled with pigment particles. Each display unit is disposed between a pair of opposed, spaced-apart substrates, and electrodes disposed on at least one substrate. When, by applying voltages onto the electrodes, an electric field is generated between the pair of substrates, the charged pigment particles in the cells migrate by attraction to the respective electrodes having opposite polarities. Thus, the locations of the pigment particles can be controlled by changing the polarities of the electrodes, thereby displaying images of the reflected light from the pigment particles or fluid.
Based on media that suspend/disperse the pigment particles in the cells, PBDs can be grouped into electrophoretic displays or dry powder type displays.
The electrophoretic displays include microcup electrophoretic displays and microcapsule electrophoretic display. In a microcup electrophoretic display, charged pigment particles (usually in white color) are dispersed in a colored fluid, which in turn, is filled in microcup display cells. The microcup display cells are then sealed between the pair of electrodes. The migrations of the pigment particles in the fluid are controlled by changing the voltage difference between the pair of electrodes, so as to achieve image displaying. For the microcup electrophoretic display, in addition to a slow response time of image displaying due to the slow migration of the pigment particles in the fluid, it is difficult to achieve the uniform dispersion of the pigment particles in the fluid, thereby reducing the uniformity of the particle filling in the display cells. In addition, a big hurdle which is difficult to overcome exists in the manufacturing process of filling the colored fluid and the pigment particles with different colors into respective display cells. If there is any misstep in the filling process, the colored fluid in the display cells may be contaminated, which results in color deviation of the display. Therefore, for the microcup electrophoretic display, the particles filling process is complicated and difficult to control, thereby increasing manufacturing costs. Also, the uniformity of the particle dispersion is yet to be further improved.
In a microcapsule electrophoretic display, two types of charged pigment particles of white and black colors with opposed polarities are filled and packaged in microcapsule display cells containing a solvent, which are sandwiched between a pair of electrodes. By changing the voltage difference between the pair of electrodes, the pigment particles can be suspended or fell in the microcapsule cells so that color image displaying can be achieved with coordination of a color filter. Similarly, the microcapsule electrophoretic display has a slow response time of image displaying due to slow motions of the pigment particles in the solvent. Further, particle aggregation exists, thereby causing the instability of the dispersion of the pigment particles in the solvent, which in turn, affects the yield rate of production. In addition, the color filter is required in this type of display to achieve color image displaying. The manufacturing process of the color filter is highly complicated and sophisticated, resulting in high manufacturing cost of the color microcapsule electrophoretic display that cannot be reduced. Also, design of the microcapsule electrophoretic display is restricted due to the existence of the color filter in the display structure. Further, the color filter reduces reflectivity of light from the environmental light source, resulting in poor chromaticity in the display.
As for a dry powder type display, each display cell is filled with two colored particles in contrast (e.g., black and white) having charges with opposite polarities, respectively. The floating state and the falling state of the different colored particles in the cells are controlled by varying external electric fields imposed on the pigment particles, thereby achieving color image displaying with coordination of the color filter. Similarly, the color filter is required in this type of display to achieve color image displaying. The manufacturing process of the color filter is highly complicated and sophisticated, resulting in high manufacturing cost of the color dry powder type display that cannot be reduced. Also, design of the dry powder type display is restricted due to the existence of the color filter in the display structure. Further, the color filter reduces reflectivity of light from the environmental light source so that the color saturation of the display is reduced. Moreover, in order to overcome the drawbacks of the slow responses of the electrophoretic displays, the pigment particles in the dry powder type displays are selected to have better flowability and floodability. As such, the pigment particles have the characteristic of fluid, and thus move fast when driven by an electric field. However, during the filling process, the pigment particles may be dispersed or spread all over the cells, i.e., the falling of the pigment particles is not along straight line even under the effect of the gravity. If the pigment particles are not uniformly filled, the display would generate color deviation in color image displaying so that yield of the display is reduced.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.